Certain surgical procedures require the resection of bone where critical soft tissues, such as tendons, ligaments and muscles, in particular the patella tendon, attach to the bone. It has been difficult to secure attachment of these soft tissues to prosthesis for multiple reasons.
First, in natural attachment to bone, there is transition region of soft tissue to bone (i.e., muscle-tendon-bone) that has a gradual change from flexible to rigid. In the reattachment of soft tissue to bone, this transition region is often lost resulting in failure of the soft tissue prosthesis interface from the flexibility of soft tissue to the very rigid metal implant.
Second, in certain procedures resection of surrounding soft tissues along with bony resections are required (i.e., resection to obtain adequate surgical margins during the removal of bone cancer such as osteosarcoma). This soft tissue resection often leaves the remaining soft tissues too short to reach their original attachment sites, even if adequate method of attachment directly to metal were available.
Currently, several methods are used to create a functional bridge between soft tissue and prosthesis, which exhibit limited success. Where there exists enough length for the soft tissue to reach the prosthesis, the soft tissue is often sutured directly to the prosthesis. Advances have been made in the material and surface treatment of the attachment sites (i.e., the use of porous or foam metals) to improve and promote the in-growth of soft tissue after surgery. However, the relative stiffness of these attachment sites compared to the soft tissue being attached continues to be a problem.
When soft tissue length is not adequate to reach the natural attachment site on the prosthesis, a graft is sometimes used to create a bridge. Autograft (via transplant or flap) can help to provide additional functional length of the soft tissue, but does not address the stiffness issue. Also, function of the graft host site is reduced. Allograft is also an option, however, again stiffness is not addressed and known issues of rejection and/or lack of integration with the graft tissue exist. Synthetic materials such as aorta-graft materials have been used to create a sleeve or bridge between the prosthesis and bone. This can address the stiffness issue at the soft tissue attachment site. However, the lack of direct integration of the synthetic material with the prosthesis means that long term loads must be borne by sutures or other suitable materials are used to secure the graft to the prosthesis. As a result, failure of the interface merely moves from the soft tissue/prosthesis interface to the graft/prosthesis interface.
In all of the above cases, the preparation and attachment of all of these grafts requires significant time and effort during the surgical setting, which exposes the patient to additional OR time in what can be an already lengthy surgical procedure.